Acylation method for an aromatic compound

ABSTRACT

The present invention concerns a process for acylation of an aromatic compound. 
     The acylation process of the invention consists of reacting the aromatic compound with an acylation agent in the presence of a zeolitic catalyst, and is characterized in that it consists of: 
     mixing the aromatic compound and the acylation compound in any manner; 
     passing said mixture over a catalytic bed comprising at least one zeolite; 
     recirculating the reaction mixture from the catalytic bed over the catalytic bed for a number of times which is sufficient to obtain the desired degree of conversion of the substrate.

This is the U.S. National Stage Application of PCT/FR97/01066 filed Jun.13, 1997.

The present invention concerns a process for the acylation of anaromatic compound, in particular an aromatic ether or thioether.

In its preferred variation, the invention concerns a process for theacylation of an aromatic ether or thioether by carboxylic acidanhydrides, preferably acetic anhydride.

More particularly, the invention is applicable to the preparation ofalkoxy- or alkylthio-aromatic alkylketones.

Conventional processes for the acylation of aromatic compounds, inparticular the ethers of phenols, use a carboxylic acid or one of itsderivatives such as the acid halide, ester or anhydride as the acylationreactant.

The reaction is generally carried out in the presence of a Lewis acidtype catalyst (for example AlCl₃) or a Brönsted acid type catalyst(H₂SO₄, HF, etc . . . ).

For about ten years, zeolites have been used as acylation catalysts.

Thus European patent EP-A-0 279 322 describes the vapour phase reactionof an aromatic compound (veratrole) with a carboxylic acid derivative inthe presence of a zeolite in its H form such as mordenite, faujasite andZSM-5.

U.S. Pat. No. 4,960,943 describes an acylation process, particularly foranisole, in the presence of zeolites which have a pore size of at least5 Angströms and which have the following formula:M_(m/z)[mMe¹O₂.nMe²O₂],qH₂O] where M is an exchangeable cation, z is thevalency of the cation and Me¹ and Me² represent the elements of theanionic skeleton, n/m is a number from 1-3000, preferably 1-2000, and qrepresents the adsorbed water.

Prins et al. have described the acetylation of anisole using aceticanhydride [9^(th) International Zeolite Congress- Montreal Congress(1992)], in the presence of zeolites such as β zeolite or US-Y zeolite.It should be noted that β zeolites can produce more interesting resultsas regards both the degree of conversion and the reaction yield.

However, the catalyst performances described are not satisfactory. Theuse of such a catalyst on an industrial scale is problematic since theproductivity of the catalyst is unsatisfactory and would thusnecessitate the use of a very large reactor.

The aim of the present invention is to provide a process which canovercome the above disadvantages.

It has now been discovered, and this constitutes the aim of the presentinvention, a process for the acylation of an aromatic compound, byreacting said compound with an acylation agent in the presence of azeolitic catalyst, characterized in that it consists of:

mixing the aromatic compound and the acylation compound in any manner;

passing said mixture over a catalytic bed comprising at least onezeolite;

recirculating the reaction mixture from the catalytic bed over thecatalytic bed for a number of times which is sufficient to obtain thedesired degree of conversion of the substrate.

The process of the invention thus uses an aromatic compound and anacylation agent.

In the following disclosure of the present invention, the term “aromaticcompound” encompasses the conventional concept of aromaticity as definedin the literature, in particular by Jerry MARCH, “Advanced OrganicChemistry”, 4^(th) edition, John Wiley and Sons, 1992, p40 ff.

The term “by an aromatic ether or thioether” means an aromatic compoundin which one hydrogen atom which is directly bonded to the aromatic ringhas been replaced by an ether or thioether group respectively.

More precisely, the present invention provides a process for acylationof an aromatic compound with general formula (I):

where:

A represents the residue of a cycle forming all or part of a carbocyclicor heterocyclic, aromatic, monocyclic or polycyclic system; said cyclicresidue may carry a radical R which represents a hydrogen atom or one ormore substituents, which may be identical or different;

n represents the number of substituents in the cycle.

The invention is particularly applicable to aromatic compounds withformula (I) in which A is the residue of a cyclic compound whichpreferably contains at least 4 atoms in the cycle, preferably 5 or 6,which may be substituted, and which represents at least one of thefollowing cycles:

an aromatic, monocyclic or polycyclic carbocycle;

an aromatic, monocyclic or polycyclic heterocycle comprising at leastone of heteroatoms O, N or S.

In more detail, without in any way limiting the scope of the invention,residue A which may optionally be substituted represents the residue:

1° of an aromatic, monocyclic or polycyclic carbocyclic compound.

The term “polycyclic carbocyclic compound” means:

a compound constituted by at least 2 aromatic carbocycles and formingortho- or ortho- and peri-condensed systems between them;

a compound constituted by at least 2 carbocycles, only one of them beingaromatic and forming ortho- or ortho- and peri-condensed systems betweenthem;

2° of an aromatic, monocyclic or polycyclic heterocyclic compound.

The term “polycyclic heterocyclic compound” defines:

a compound constituted by at least 2 heterocycles containing at leastone heteroatom in each cycle, at least one of the two cycles beingaromatic and forming ortho- or ortho- and peri-condensed systems betweenthem;

a compound constituted by at least one hydrocarbon cycle and at leastone heterocycle, at least one of the cycles being aromatic and formingortho- or ortho-and peri-condensed systems between them;

3° of a compound constituted by linked cycles as defined in paragraphs 1and/or 2 linked together by:

a valence bond;

an alkylene or alkylidene radical containing 1 to 4 carbon atoms,preferably a methylene radical or an isopropylidene radical;

one of the following groups:

in these formulae, R₀ represents a hydrogen atom or an alkyl radicalcontaining 1 to 4 carbon atoms, or a cyclohexyl or phenyl radical.

More particularly, residue A which may optionally be substitutedrepresents the residue:

of an aromatic carbocyclic monocyclic compound such as benzene, toluene,isobutylbenzene, anisole, thioanisole, phenetole or veratrole, guaiacolor guetol;

of an aromatic condensed polycyclic compound, such as naphthalene or2-methoxynaphthalene;

of an aromatic carbocyclic, non condensed polycyclic compound such asphenoxybenzene;

of a partially aromatic carbocyclic condensed polycyclic compound suchas tetrahydronaphthalene or 1,2-methylenedioxybenzene;

of a partially aromatic carbocyclic non condensed polycyclic compoundsuch as cyclohexylbenzene;

of an aromatic heterocyclic monocyclic compound such as pyridine, furanor thiophene;

of a partially heterocyclic aromatic condensed polycyclic compound suchas quinoline, indole or benzofuran;

of a partially heterocyclic aromatic, non condensed polycyclic compoundsuch as phenylpyridines, or naphthylpyridines;

of a partially heterocyclic, partially aromatic condensed polycycliccompound such as tetrahydroquinoline;

of a partially heterocyclic, partially aromatic, non condensedpolycyclic compound such as cyclohexylpyridine.

In the process of the invention, an aromatic compound with formula (I)is preferably used in which A represents an aromatic nucleus, preferablya benzenic or naphthalene nucleus.

The aromatic compound with formula (I) can carry one or moresubstituents.

The number of substituents present in the cycle depend on the carboncondensation of the cycle and the presence or otherwise of unsaturationsin the cycle.

The maximum number of substituents which can be carried by a cycle canreadily be determined by the skilled person.

In the present description, the term “several” generally means less than4 substituents on one aromatic nucleus.

Examples of substituents are given below but these are not limiting.

Radicals R, which may be identical or different, preferably representone of the following groups:

a hydrogen atom;

a linear or branched alkyl radical containing 1 to 6 carbon atoms,preferably 1 to 4 carbon atoms, such as methyl, ethyl, propyl,isopropyl, butyl, isobutyl, sec-butyl, tert-butyl;

a linear or branched alkenyl radical containing 2 to 6 carbon atoms,preferably 2 to 4 carbon atoms, such as vinyl, allyl;

a linear or branched alkoxy radical containing 1 to 6 carbon atoms,preferably 1 to 4 carbon atoms, such as methoxy, ethoxy, propoxy,isopropoxy, or butoxy radicals, or an alkenyloxy radical, preferably anallyloxy or a phenoxy radical;

a cyclohexyl, phenyl or benzyl radical;

an acyl group containing 2 to 6 carbon atoms;

a radical with formula:

—R₁—OH

—R₁—COOR₂

—R₁—CHO

—R₁—NO₂

—R₁—CN

—R₁—N(R₂)₂

—R₁—CO—N(R₂)₂

—R₁—X

—R₁—CF₃

in said formulae, R₁ represents a valence bond or a divalent, linear orbranched, saturated or unsaturated hydrocarbon radical containing 1 to 6carbon atoms, such as methylene, ethylene, propylene, isopropylene, orisopropylidene; radicals R₂, which may be identical or different,represent a hydrogen atom or a linear or branched alkyl radicalcontaining 1 to 6 carbon atoms; X represents a halogen atom, preferablya chlorine, bromine or fluorine atom;

two radicals R placed on two neighbouring carbon atoms may together formwith the carbon atoms they carry a cycle containing 5 to 7 atoms,optionally comprising a further heteroatom.

When n is greater than or equal to 2, two radicals R and the 2successive atoms of the aromatic cycle can be bonded together by analkylene, alkenylene or alkenylidene radical containing 2 to 4 carbonatoms to form a saturated, unsaturated or aromatic heterocyclecontaining 5 to 7 carbon atoms. One or more carbon atoms can be replacedby a further heteroatom, preferably oxygen or sulphur. Thus radicals Rcan represent a methylenedioxy or ethylenedioxy radical or amethylenedithio or ethylenedithio radical.

The present invention is particularly applicable to aromatic compoundswith formula (I) in which radicals R represent an electron-donatinggroup.

In the present description, the term “electron-donating group” means agroup as defined by H. C. BROWN in the book by Jerry MARCH, “AdvancedOrganic Chemistry”, Chapter 9, pages 243 and 244 (1985).

The aromatic compounds which are preferably used have formula (Ia):

where:

A represents the residue of a cycle forming all or part of an aromatic,monocyclic or polycyclic, carbocyclic or heterocyclic system: saidcyclic residue can carry a radical R representing a hydrogen atom or oneor more electron-donating substituents, which may be identical ordifferent;

n represents the number of substituents in the cycle.

Examples of preferred electron-donating groups R are:

a linear or branched alkyl radical containing 1 to 6 carbon atoms,preferably 1 to 4 carbon atoms, such as methyl, ethyl, propyl,isopropyl, butyl, isobutyl, sec-butyl, tert-butyl;

a linear or branched alkenyl radical containing 2 to 6 carbon atoms,preferably 2 to 4 carbon atoms, such as vinyl, allyl;

a cyclohexyl, phenyl or benzyl radical;

a linear or branched alkoxy radical containing 1 to 6 carbon atoms,preferably 1 to 4 carbon atoms, such as methoxy, ethoxy, propoxy,isopropoxy, or butoxy radicals, or an alkenyloxy radical, preferably anallyloxy or a phenoxy radical;

a radical with formula:

—R₁—OH

—R₁—N(R₂)₂

in said formulae, R₁ represents a valence bond or a divalent, linear orbranched, saturated or unsaturated hydrocarbon radical containing 1 to 6carbon atoms such as methylene, ethylene, propylene, isopropylene, orisopropylidene; radicals R₂, which may be identical or different,represent a hydrogen atom or a linear or branched alkyl radicalcontaining 1 to 6 carbon atoms;

two radicals R may be bonded together to form alkylenedioxy oralkylenedithio radicals, preferably a methylenedioxy, ethylenedioxy,methylenedithio or ethylenedithio radical.

In formula (Ia), n is a number which is less than or equal to 4,preferably 1 or 2.

As mentioned above, the process of the invention is particularlysuitable for the acylation of aromatic ethers and thioethers.

The preferred formula for said compounds is:

where:

Y represents an oxygen atom or a sulphur atom;

A represents the residue of a cycle forming all or a portion of anaromatic, monocyclic or polycyclic carbocyclic system comprising atleast one group YR′: said cyclic residue may carry one or moresubstituents;

R represents one or more substituents, which may be identical ordifferent;

R′ represents a hydrocarbon radical containing 1 to 24 carbon atoms,which can be a linear or branched, saturated or unsaturated acyclicaliphatic radical; a saturated, unsaturated or aromatic, monocyclic orpolycyclic cycloaliphatic radical; or a saturated or unsaturated, linearor branched aliphatic radical carrying a cyclic substituent;

R′ and R can form a cycle which optionally comprises a furtherheteroatom;

n is a number which is less than or equal to 4.

For simplification in the present text, the term “alkoxy or thioether”respectively designates R′—O— or R′—S— type groups where R′ has themeaning given above. R′ can thus represent both a saturated, unsaturatedor aromatic, acyclic or cycloaliphatic aliphatic radical and a saturatedor unsaturated aliphatic radical carrying a cyclic substituent.

The aromatic ether or thioether used in the process of the invention hasformula (I′) where R′ represents a linear or branched, saturated orunsaturated, acyclic aliphatic radical.

More preferably, R′ represents a linear or branched alkyl radicalcontaining 1 to 12 carbon atoms, preferably 1 to 6 carbon atoms: thehydrocarbon chain can optionally be interrupted by a heteroatom (forexample oxygen), by a functional group (for example —CO—) and/or maycarry substituents (for example, one or more halogen atoms).

The linear or branched, saturated or unsaturated, acyclic aliphaticradical can optionally carry a cyclic substituent. The term “cycle”preferably means a saturated, unsaturated or aromatic carbocyclic cycle,preferably cycloaliphatic or aromatic, particularly cycloaliphaticcontaining 6 carbon atoms in the cycle, or benzenic.

The acyclic aliphatic radical can be connected to the cycle by a valencebond, a heteroatom or a functional group and examples are given below.

The cycle can optionally be substituted and examples of cyclicsubstituents are, among others, substituents such as R, the meaning ofwhich has been defined for formula (I′).

R′ can also represent a carbocyclic radical which is saturated or whichcomprises 1 or 2 unsaturations in the cycle, generally containing 3 to 8carbon atoms, preferably 6 carbon atoms in the cycle; said cycle can besubstituted by substituents such as R.

R′ can also represent an aromatic carbocyclic radical, preferablymonocyclic generally containing at least 4 carbon atoms, preferably 6carbon atoms in the cycle; said cycle can be substituted by substituentssuch as R

In general formula (I′) for aromatic ethers or thioethers, residue A canrepresent the residue of an aromatic monocyclic carbocyclic compoundcontaining at least 4 carbon atoms, preferably 6 carbon atoms, or theresidue of a polycyclic carbocyclic compound which can be constituted byat least two aromatic carbocycles and form between them ortho- or ortho-and peri-condensed systems or by at least 2 carbocycles, at least one ofthem being aromatic and forming between them ortho- or ortho- andperi-condensed systems. A naphthalenic residue can be cited inparticular.

Residue A can carry one or more substituents on the aromatic nucleus.

Reference can be made to the examples of substituents given for formula(I) but this list is not limiting. Any substituent can be present on thecycle provided that it does not interfere with the desired product.

Since residue A can, among others, carry several alkoxy groups, it ispossible to use the process of the invention to acylate polyalkoxylatedcompounds.

In formula (I′), R more preferably represents one of the following atomsor groups:

a linear or branched alkyl radical containing 1 to 6 carbon atoms,preferably 1 to 4 carbon atoms, such as methyl, ethyl, propyl,isopropyl, butyl, isobutyl, sec-butyl or tert-butyl;

a linear or branched alkoxy radical containing 1 to 6 carbon atoms,preferably 1 to 4 carbon atoms, such as methoxy, ethoxy, propoxy,isopropoxy, butoxy, isobutoxy, sec-butoxy, or tert-butoxy;

a halogen atom, preferably a fluorine, chlorine or bromine atom, or atrifluoromethyl radical.

The process of the invention is of particular application to aromaticethers or thioiethers with formula (I′a):

where:

n is a number which is less than or equal to 4, preferably 0 or 1;

Y represents an oxygen atom or a sulphur atom;

radical R′ represents a linear or branched alkyl radical containing 1 to6 carbon atoms, preferably 1 to 4 carbon atoms, such as methyl, ethyl,propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl or a phenylradical;

radical(s) R, which may be identical or different, represent one of thefollowing atoms or groups:

a hydrogen atom;

a linear or branched alkyl radical containing 1 to 6 carbon atoms,preferably 1 to 4 carbon atoms, such as methyl, ethyl, propyl,isopropyl, butyl, isobutyl, sec-butyl, or tert-butyl;

a linear or branched alkenyl radical containing 2 to 6 carbon atoms,preferably 2 to 4 carbon atoms, such as vinyl, allyl;

a linear or branched alkoxy radical containing 1 to 6 carbon atoms,preferably 1 to 4 carbon atoms, such as methoxy, ethoxy, propoxy,isopropoxy, or butoxy radicals, or an alkenyloxy radical, preferably anallyloxy or a phenoxy radical;

a cyclohexyl, phenyl or benzyl radical;

a an acyl group containing 2 to 6 carbon atoms;

a radical with formula:

—R₁—OH

—R₁—COOR₂

—R₁—CHO

—R₁—NO₂

—R₁—CN

—R₁—N(R₂)₂

—R₁—CO—N(R₂)₂

—R₁—X

—R₁—CF₃

in said formulae, R₁ represents a valence bond or a divalent, linear orbranched, saturated or unsaturated hydrocarbon radical containing 1 to 6carbon atoms such as methylene, ethylene, propylene, isopropylene, orisopropylidene; radicals R₂, which may be identical or different,represent a hydrogen atom or a linear or branched alkyl radicalcontaining 1 to 6 carbon atoms; X represents a halogen atom, preferablya chlorine, bromine or fluorine atom;

radicals R and R′ placed on two neighbouring carbon atoms may togetherform with the carbon atoms they carry a cycle containing 5 to 7 atoms,optionally comprising a further heteroatom.

When n is greater than or equal to 1, radicals R′ and R and the 2successive atoms of the benzenic cycle can be bonded together to form analkylene, alkenylene or alkenylidene radical containing 2 to 4 carbonatoms to form a saturated, unsaturated or aromatic heterocyclecontaining 5 to 7 atoms. One or more carbon atoms can be replaced by afurther heteroatom, preferably oxygen or sulphur. Thus radicals OR′ andR can represent a methylenedioxy or ethylenedioxy radical and radicalsSR′ and R can represent a methylenedithio or ethylenedithio radical.

In formula (I′a), R′ preferably represents a linear or branched alkylradical containing 1 to 6 carbon atoms, preferably a methyl or ethylradical or a phenyl radical.

The benzenic nucleus carries one or more substituents R which may beidentical or different. R preferably represents a linear or branchedalkyl radical containing 1 to 6 carbon atoms, preferably a methyl orethyl radical; or a linear or branched alkoxy radical containing 1 to 4carbon atoms, preferably a methoxy or ethoxy radical.

The process of the invention is particularly applicable to aromaticethers and thioethers with formula (I′) or (I′a) where:

n equals 0 or 1;

R′ represents a linear or branched alkyl radical containing 1 to 6carbon atoms or a phenyl radical, preferably a methyl or ethyl radical;

R represents a linear or branched alkyl radical containing 1 to 6 carbonatoms, preferably a methyl or ethyl radical; or a linear or branchedalkoxy radical containing 1 to 4 carbon atoms, preferably a methoxy orethoxy radical;

radicals YR′ and R form a methylenedioxy, ethylenedioxy, methylenedithioor ethylenedithio radical.

Particular illustrations of compounds with formula (I) or (I′) are:

aromatic compounds such as benzene, toluene, fluorobenzene,chlorotoluenes, fluorotoluenes, trifluoromethoxybenzene,trichloromethoxybenzene, or trifluoromethylthiobenzene;

aromatic amine-containing compounds such as aniline;

phenolic compounds such as phenol, o-cresol, guaiacol, guetol,α-naphthol, or β-naphthol;

monoethers such as anisole, ethoxybenzene (phenetole), propoxybenzene,isopropoxybenzene, butoxybenzene, isobutoxybenzene,1-methoxynaphthalene, 2-methoxynaphthalene, or 2-ethoxynaphthalene;substituted monoethers such as 2-chloroanisole, 3-chloroanisole,2-bromoanisole, 3-bromoanisole, 2-methylanisole, 3-methylanisole,2-ethylanisole, 3-ethylanisole, 2-isopropylanisole, 3-isopropylanisole,2-propylanisole, 3-propylanisole, 2-allylanisole, 2-butylanisole,3-butylanisole, 2-benzylanisole, 2-cyclohexylanisole,1-bromo-2-ethoxybenzene, 1-bromo-3-ethoxybenzene,1-chloro-2-ethoxybenzene, 1-chloro-3-ethoxybenzene,1-ethoxy-2-ethylbenzene, 1-ethoxy-3-ethylbenzene,1-methoxy-2-allyloxybenzene, 2,3dimethylanisole, or 2,5-dimethylanisole;

diethers such as veratrole, 1,3-dimethoxybenzene, 1,4dimethoxybenzene,1,2-diethoxybenzene, 1,3-diethoxybenzene, 1,2-dipropoxybenzene,1,3-dipropoxybenzene, 1,2-methylenedioxybenzene, or1,2-ethylenedioxybenzene;

triethers such as 1,2,3-trimethoxybenzene, 1,3,5-trimethoxybenzene, or1,3,5-triethoxybenzene;

thioethers such as thioanisole, o-thiocresol, m-thiocresol,p-thiocresol, 2-thioethylnaphthalene, S-phenylthioacetate,3-(methylmercapto)aniline, or phenylthiopropionate.

Benzene, toluene, isobutylbenzene, anisole, phenetole, veratrole,1,2-methylenedioxybenzene, 2-methoxynaphthalene and thioanisole arecompounds to which the process of the invention is particularlyapplicable.

Regarding the acylation reactant, carboxylic acids and their halide oranhydride derivatives are used, preferably anhydrides.

More particularly, the acylation reactant has formula (II):

where:

R₃ represents:

a linear or branched, saturated or unsaturated aliphatic radicalcontaining 1 to 24 carbon atoms; a monocyclic or polycyclic, saturated,unsaturated or aromatic cycloaliphatic radical containing 3 to 8 carbonatoms; or a linear or branched, saturated or unsaturated aliphaticradical carrying a cyclic substituent;

X′ represents:

a halogen atom, preferably a chlorine or bromine atom;

a hydroxyl group;

a —O—CO—R₄ radical, where R₄, which may be identical to or differentfrom R₃, has the same meaning as R₃: R₃ and R₄ may together form adivalent linear or branched, saturated or unsaturated aliphatic radicalcontaining at least 2 carbon atoms.

Reference should be made to the above description for the meaning of theterm “cyclic substituent”.

More preferably, R₃ represents a linear or branched alkyl radicalcontaining 1 to 12 carbon atoms, preferably 1 to 6 carbon atoms: thehydrocarbon chain can optionally be interrupted by a heteroatom (forexample oxygen), by a functional group (for example —CO—) and/or maycarry a substituent (for example a halogen or a CF₃ group).

R₃ preferably represents an alkyl radical containing 1 to 4 carbonatoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl,sec-butyl, or tert-butyl.

R₃ also represents an alkenyl radical containing 2 to 10 carbon atoms,such as vinyl, propen-yl, buten-yl, penten-yl, hexen-yl, octen-yl, ordecen-yl.

Preferably, radical R₃ also represents a phenyl radical which canoptionally be substituted. Any substituent can be present on the cycleprovided that it does not interfere with the desired product.

Particular examples of substituents are:

a linear or branched alkyl radical containing 1 to 6 carbon atoms,preferably 1 to 4 carbon atoms, such as methyl, ethyl, propyl,isopropyl, butyl, isobutyl, sec-butyl, or tert-butyl;

a linear or branched alkoxy radical containing 1 to 6 carbon atoms,preferably 1 to 4 carbon atoms such as methoxy, ethoxy, propoxy,isopropoxy, butoxy, isobutoxy, sec-butoxy, or tert-butoxy;

a hydroxyl group;

a halogen atom, preferably a fluorine, chlorine or bromine atom.

Preferred acylation agents are acid anhydrides. More particularly, theyhave formula (II) where R₃ and R₄ are identical and represent an alkylradical containing 1 to 4 carbon atoms or a phenyl radical.

When the acylation agent is an acid halide, it preferably has formula(II) where X′ represents a chlorine atom and R₃ represents a methyl,ethyl or phenyl radical.

Particular illustrative examples of acylation agents with formula (II)are:

acetic anhydride;

propanoic anhydride

butyric anhydride;

isobutyric anhydride;

trifluoroacetic anhydride;

benzoic anhydride;

monochloroacetyl anhydride;

dichloroacetyl anhydride;

acetyl chloride;

monochloroacetyl chloride;

dichloroacetyl chloride;

propanoyl chloride;

isobutanoyl chloride;

pivaloyl chloride;

stearoyl chloride;;

crotonyl chloride;

benzoyl chloride;

chlorobenzoyl chlorides;

p-nitrobenzoyl chloride;

methoxybenzoyl chlorides;

naphthoyl chlorides;

acetic acid;

benzoic acid.

Preferred acylation agents are acetic, propanoic, benzoic,monochloroacetyl, and dichloroacetyl anhydride, also benzoyl chloride.

In accordance with the invention, the acylation reaction is carried outin the presence of a zeolitic catalyst.

The term “zeolite” means a crystallised tectosilicate of natural orsynthetic origin, the crystals of which result from thethree-dimensional assembly of SiO₄ and TO₄ tetrahedra: T represents atrivalent element such as aluminium, gallium, boron, or iron, preferablyaluminium.

Aluminosilicate type zeolites are the most common.

The crystalline framework of a zeolite has a system of cavities linkedtogether by channels, termed pores, of a well defined diameter.

Zeolites can have a one-dimensional, two-dimensional orthree-dimensional network of channels.

The process of the invention uses a natural or a synthetic zeolite.

Examples of natural zeolites which can be used are: chabazite,clinoptilolite, erionite, phillipsite, and offretite.

Synthetic zeolites are also suitable for use in the process of theinvention.

Examples of zeolites with a one-dimensional network are ZSM-4 zeolite, Lzeolite, ZSM-12 zeolite, ZSM-22 zeolite, ZSM-23 zeolite, and ZSM-48zeolite.

Preferred examples of zeolites with a two-dimensional network are βzeolite, mordenite, and ferrierite.

Particular examples of zeolites with a three-dimensional network are Yzeolite, X zeolite, ZSM-5 zeolite, ZSM-11 zeolite, and offretite.

Preferably, synthetic zeolites are used, more particularly zeolites inthe following forms:

mazzite with a Si/Al molar ratio of 3.4;

L zeolite with a Si/Al molar ratio of 1.5 to 3.5;

mordenite with a Si/Al molar ratio of 5 to 15;

ferrierite with a Si/Al molar ratio of 3 to 10;

offretite with a Si/Al molar ratio of 4 to 8.5;

β zeolites with a Si/Al molar ratio of more than 8, preferably in therange 10 to 100, more preferably between 12 and 50;

Y zeolites, in particular the zeolites obtained after dealumination (forexample hydrotreatment, washing using hydrochloric acid or treatmentwith SiCl₄), more particularly US-Y zeolites with a Si/Al molar ratio ofmore than 3, preferably in the range 6 to 60;

X zeolite of faujasite type with a Si/Al molar ratio of 0.7 to 1.5;

ZSM-5 zeolite or aluminium silicalite with a Si/Al molar ratio of 10 to500;

ZSM-11 with a Si/Al molar ratio of 5 to 30;

mesoporous MCM type zeolite, more particularly MCM-22 and MCM-41 with aSi/Al molar ratio which is in the range 10 to 100, preferably in therange 15 to 40.

Of all these zeolites, β and Y zeolites are preferably used in theprocess of the invention.

The zeolites used in the process of the invention are known productsdescribed in the literature [see “Atlas of Zeolite Structure Types” byW. M. Meier and D. H. Olson, published by the Structure Commission ofthe International Zeolite Association (1978)].

Commercially available zeolites can be used, or they can be synthesisedusing processes described in the literature.

Reference can be made to the Atlas mentioned above, more particularlyfor the preparation of:

L zeolite from the publication by R. M. Barrer et al., Z. Kristallogr.,128, pp. 352 (1969);

ZSM-12 zeolite from U.S. Pat. No. 3,832,449 and the article by LaPierreet al., Zeolites 5, pp 346 (1985);

ZSM-22, in the publication by G. T. Kokotailo et al., Zeolites 5, pp.349 (1985);

of ZSM-23 zeolite, from U.S. Pat. No. 4,076,842 and the article by A. C.Rohrman et al., Zeolites 5, pp. 352 (1985);

ZSM-48 zeolite, from the work by J. L. Schlenker et al., Zeolites 5, pp.355 (1985)

β zeolite, from U.S. Pat. No. 3,308,069 and the article by P. Caullet etal., Zeolites 12, 240 (1992);

mordenite, from the work by Itabashi et al., Zeolites 6, pp. 30 (1986);

X and Y zeolites respectively from U.S. Pat. No. 2,882,244 and U.S. Pat.No. 3,130,007;

ZSM5 zeolite, from U.S. Pat. No. 3,702,886 and the article by V. P.Shiralkar et al., Zeolites 9, pp. 363 (1989);

ZSM-11 zeolite, from the work by I. D. Harrison et al., Zeolites 7, p.21 (1987);

mesoporous MCM type zeolite, from the article by Beck et al., J. Am.Chem. Soc., 114, pp. 10834-43 (1992).

The zeolite constitutes the catalytic phase. It can be used alone ormixed with an inorganic matrix. In the description, the term “catalyst”refers to the catalyst which is all zeolite or to a mixture with amatrix prepared using the techniques known to the skilled person.

To this end, the matrix can be selected from oxides of metals such asaluminium, silicon and/or zirconium oxides, or from clays, moreparticularly kaolin, talc or montmorillonite.

The amount of active phase in the catalyst can be 5% to 100% of theweight of the catalyst.

The catalysts can be in different forms in the process of the invention:powder, formed products such as granulates (for example extrudates orspherules), or pellets, obtained by extrusion, moulding, compacting orany other type of known process. In practice, on an industrial scale,these are the forms of granulates or spherules which have the mostadvantages as regards efficacity and ease of use.

In accordance with the invention, the acylation reaction is carried outusing a process for recirculation of the reaction mixture over a fixedbed of catalyst.

The process is begun by forming the mixture of the aromatic compound andthe acylation agent in any manner.

Thus, the aromatic compound and the acylation agent can be mixed in amixing zone and the mixture obtained can then be sent over the catalyticbed.

In a further variation, one of the reactants (aromatic compound oracylation agent) can be introduced and sent over the catalytic bed andthen the other reactant can be added all at once or gradually when thedesired reaction temperature is reached. In this way, and preferably,the aromatic compound is introduced then the acylation agent isgradually added.

The invention encompasses introducing the mixture of reactants thenadding one of two other reactants at the desired temperature so as toobtain the desired aromatic compound/acylation agent ratio.

The final ratio between the number of moles of aromatic compound and thenumber of moles of acylation agent can vary widely. Thus the ratio canbe from 0.1 to 20, preferably between 0.5 and 10.

In a preferred implementation of the invention, in order to increase theyield and maintain the activity of the catalyst, an excess of aromaticcompound is used. Thus an aromatic compound/acylation agent molar ratiois selected which is at least 1, preferably in the range 1 to 20, morepreferably in the range 1 to 10.

One of the reactants is generally used as the reaction solvent, but theuse of an organic solvent, the nature of which is determined by theskilled person, is not excluded.

In a preferred implementation of the process of the invention, thetemperature of the mixture is brought to the temperature at which thereaction is carried out.

The temperature at which the acylation reaction is carried out dependson the reactivity of the starting substrate and that of the acylationagent.

It is between 20° C. and 300° C., preferably between 40° C. and 200° C.,and more preferably between 40° C. and 150° C.

The reactants are passed over a catalytic bed comprising at least onezeolite.

The quantity of catalyst used in the process of the invention can varybetween wide limits.

The catalyst can represent 0.01% to 50%, preferably 1.0% to 20%, byweight with respect to the aromatic ether or thioether used.

The reaction is generally carried out at atmospheric pressure but loweror higher pressures can also be suitable. Autogenous pressure is usedwhen the temperature of the reaction is more than the boiling point ofthe reactants and/or products.

The reaction mixture preferably passes through the catalytic bed frombottom to top and is returned from the outlet to the reactant mixingzone to recycle a sufficient number of times to obtain the desireddegree of conversion of the substrate, preferably more than 20%, morepreferably in the range 50% to 100%. The degree of conversion of thesubstrate is defined as the ratio between the number of moles oftransformed substrate and the number of moles of substrate introduced.

The linear velocity of the liquid stream over the catalytic bedadvantageously varies between 0.1 and 10 cm/s, preferably between 0.1and 5 cm/s.

The residence time for the stream of material on the catalytic bed isbetween 15 min and 15 hours, for example, preferably between 30 min and10 hours.

When the reaction is over, a liquid phase comprising the acylatedaromatic compound is obtained which can be recovered conventionally, bydistillation or recrystallisation from a suitable solvent, after priorelimination of the excess reactants.

The accompanying FIG. 1 shows a preferred embodiment of the invention,which is given for better comprehension of the invention.

In a reactor (1), the aromatic compound (preferably an aromatic ether orthioether) and the acylation agent are mixed. The reactor can be stirredor not stirred, provided with inlet valves for the reactants and outletvalves and provided with a heating means or provided with a doubleenvelope for heating the mixture by circulating a liquid at the suitabletemperature. Stirring, which is not obligatory, can be carried out usingan Impeller® (2).

Aromatic compound (3) and acylation agent (4) are introduced into thereactor (1).

The reaction mixture is sent, using any appropriate means, in particulara centrigal pump (5), to the bottom (6) of a tube reactor (7) comprisingthe solid zeolitic catalyst disposed in a fixed bed (8).

At the reactor outlet (9), the reaction mixture is sent to reactor (1)via a conduit (10) and thus circulates in a closed loop.

When the reaction is over, the reaction mixture is recovered by emptyingmixer (1) via a valve (11) which is not shown in the diagram.

The process of the invention is particularly suitable for preparing4-methoxyacetophenone, usually known as acetoanisole, by acetylation ofanisole.

One advantage of the process of the invention is that the acylationreaction is carried out without O-dealkylation of the starting aromaticether.

The following examples illustrate the invention without limiting it inany way.

In the examples, the yields quoted are defined as follows:${\text{Yield:~~}{RR}_{AA}} = {\frac{\begin{matrix}\text{number~~of~~moles~~of~~acylated} \\\text{aromatic~~compound~~formed}\end{matrix}}{\begin{matrix}\text{number~~of~~moles~~of~~acylation} \\\text{agent~~introduced}\end{matrix}}\quad \%}$

EXAMPLES

The operating protocol followed in the different examples is givenbelow. Reference should be made to FIG. 1.

Zeolitic catalyst was charged into a stainless steel reactor (7) to formthe catalytic bed which rested on a layer (about 20 mm thick) of glassbeads, and the top of the bed was also covered with about 20 mm of glassbeads with a diameter of 5 mm.

Anisole was charged at ambient temperature into a 3 liter doubleenvelope Sovirel® reactor; stirring was begun (40 rpm) and it wascirculated over the fixed bed for 15 min; the flow rate was maintainedat 60 l/h for the whole duration of the reaction. The reaction wasobserved to be slightly exothermal.

The reaction mixture was heated using a thermostatted bath to produce aconstant temperature of 90° C. at the top of the catalytic bed.

When a temperature of 90° C. had been produced in the bed, aceticanhydride was added over 4 hours, keeping the medium circulating.

After addition, the reaction was kept going for 3 hours at 90° C. (i.e.,7 hours in total).

When the reaction was over, the temperature was allowed to fall to 60°C., and the apparatus was emptied. Nitrogen was blown through the fixedbed for 20 minutes.

Example 1

In this example, anisole was acetylated.

A catalyst comprising 40% of binder (alumina) and 60% of a β zeolitesold by PQ was used.

The zeolite used was a zeolite with a Si/Al ratio of 12.5.

It was used in an amount of 21% with respect to the acetic anhydride,i.e., 225 g.

The number of moles of anisole was 20.9 mol and that of the aceticanhydride was 10.45 mol: the anisole/acetic anhydride molar ratio was2/1.

The reaction temperature was 90° C., as mentioned above.

Gas chromatography showed a yield (RR) of 75% of 4-methoxyacetophenoneafter 7 hours.

Examples 2 to 5

The above operation was repeated 4 times using the same catalytic bed asabove.

The yield for each operation (RR) was respectively 68%, 65%, 62% and59%.

Example 6

In this example, veratrole was acetylated.

A catalyst comprising 20% of binder (alumina) and 80% of a Y CBV780zeolite sold by PQ was used.

It was used in an amount of 21% with respect to the acetic anhydride,i.e., 225 g.

The veratrole/acetic anhydride molar ratio was 2/1.

The reaction temperature was 90° C., as mentioned above.

Gas chromatography showed a yield (RR) of 72% of3,4-dimethoxyacetophenone after 6 hours.

Example 7

In this example, toluene was acetylated, as in Example 1: the differencewas that the reactor was larger, namely 20 l.

A catalyst comprising 40% of binder (alumina) and 60% of a β zeolitesold by PQ was used.

The zeolite used was a zeolite with a Si/Al ratio of 12.5.

It was used in an amount of 50% with respect to the acetic anhydride,i.e., 562 g.

The number of moles of toluene was 110 mol and that of the aceticanhydride was 11.00 mol: the toluene/acetic anhydride molar ratio was10.

The reaction temperature was 150° C., as mentioned above.

Gas chromatography showed a yield (RR) of 63% of 4-methoxyacetophenoneafter 10 hours.

Example 8

In this example, isobutylbenzene was acetylated.

A catalyst comprising 40% of binder (alumina) and 60% of a β zeolitesold by PQ was used.

The zeolite used was a zeolite with a Si/Al ratio of 12.5.

It was used in an amount of 60% with respect to the acetic anhydride,i.e., 672 g.

The number of moles of isobutylbenzene was 143 mol and that of theacetic anhydride was 11 mol: the isobutylbenzene /acetic anhydride molarratio was 13.

The reaction temperature was 150° C., as mentioned above.

Gas chromatography showed a yield (RR) of 75% of 4-isobutylacetophenoneafter 7 hours.

What is claimed is:
 1. A process for the acylation of an aromaticcompound by reacting said compound with an acylation agent in thepresence of a zeolitic catalyst, comprising: mixing the aromaticcompound and the acylation compound thereby forming a reaction mixture;passing said mixture over a catalytic bed comprising at least onezeolite; recirculating the reaction mixture from the catalytic bed overthe catalytic bed.
 2. A process according to claim 1, wherein thearomatic compound has formula (I):

where: A represents the residue of a cycle forming all or part of acarbocyclic or heterocyclic, aromatic, monocyclic or polycyclic system;said cyclic residue carries a radical R which represents a hydrogen atomor one or more substituents, which may be identical or different; nrepresents the number of substituents in the cycle.
 3. A processaccording to claim 2, wherein the aromatic compound has formula (I) inwhich residue A, which is optionally substituted, represents theresidue: 1° of an aromatic, monocyclic or polycyclic carbocycliccompound, 2° of an aromatic, monocyclic or polycyclic heterocycliccompound, 3° of a compound constituted by linking cycles of an aromatic,monocyclic, polycyclic carbocyclic or heterocyclic compound linkedtogether by: a valence bond; an alkylene or alkylidene radicalcontaining 1 to 4 carbon atoms; one of the following groups:

in these formulae, R₀ represents a hydrogen atom or an alkyl radicalcontaining 1 to 4 carbon atoms, or a cyclohexyl or phenyl radical.
 4. Aprocess according to claim 2, wherein the aromatic compound has formula(I) in which radical(s) R, which may be identical or different,represent one of the following groups: a hydrogen atom; a linear orbranched alkyl radical containing 1 to 6 carbon atoms; a linear orbranched alkenyl radical containing 2 to 6 carbon atoms; a linear orbranched alkoxy radical containing 1 to 6 carbon atoms; a cyclohexyl,phenyl or benzyl radical; an acyl group containing 2 to 6 carbon atoms;a radical with formula: —R₁—OH —R₁—COOR₂ —R₁—CHO —R₁—NO₂ —R₁—CN—R₁—N(R₂)₂ —R₁—CO—N(R₂)₂ —R₁—X —R₁—CF₃ in said formulae, R₁represents avalence bond or a divalent, linear or branched, saturated or unsaturatedhydrocarbon radical containing 1 to 6 carbon atoms; radicals R₂, whichmay be identical or different, represent a hydrogen atom or a linear orbranched alkyl radical containing 1 to 6 carbon atoms; X represents ahalogen atom, or fluorine atom; two radicals R placed on two neighboringcarbon atoms may together form with the carbon atoms they carry a cyclecontaining 5 to 7 atoms.
 5. A process according to claim 2, wherein thearomatic compound has formula (I) where n is greater than or equal to 2,two radicals R and the two successive atoms of the aromatic cycle can bebonded together by an alkylene, alkenylene or alkenylidene radicalcontaining 2 to 4 carbon atoms to form a saturated, unsaturated oraromatic heterocycle containing 5 to 7 carbon atoms: one or more carbonatoms can be replaced by a further heteroatom.
 6. A process according toclaim 1, wherein the aromatic compound has formula (Ia):

where: A represents the residue of a cycle forming all or part of anaromatic, monocyclic or polycyclic, carbocyclic or heterocycle system:said cyclic residue can carry a radical R representing a hydrogen atomor one or more electron donating substituents, which may be identical ordifferent; n represents the number of substituents in the cycle.
 7. Aprocess according to claim 6, wherein the aromatic compound has formula(Ia) in which: radical(s) R, which may be identical or different,represent one of the following groups: a linear or branched alkylradical containing 1 to 6 carbon atoms; a linear or branched alkenylradical containing 2 to 6 carbon atoms, a linear or branched alkoxyradical containing 1 to 6 carbon atoms, a radical with formula: —R₁—OH—R₁—N(R₂)₂ in said formulae, R₁represents a valence bond or a divalent,linear or branched, saturated or unsaturated hydrocarbon radicalcontaining 1 to 6 carbon atoms, radicals R₂, which may be identical ordifferent, represent a hydrogen atom or a linear or branched alkylradical containing 1 to 6 carbon atoms; radicals R may be bondedtogether to form alkylenedioxy or alkylenedithio radicals; n is a numberwhich is less than or equal to
 4. 8. A process according to claim 1,wherein the aromatic compound is an aromatic ether or thioether withformula (I′):

where: Y represents an oxygen atom or a sulphur atom; A represents theresidue of a cycle forming all or a portion of an aromatic, monocyclicor polycyclic carbocyclic system comprising at least one group YR′: saidcyclic residue may carry one or more substituents; R represents one ormore substituents, which may be identical or different; R′represents ahydrocarbon radical containing 1 to 24 carbon atoms, which can be alinear or branched, saturated or unsaturated acyclic aliphatic radical;a saturated, unsaturated or aromatic, monocyclic or polycycliccycloaliphatic radical; or a saturated or unsaturated, linear orbranched aliphatic radical carrying a cyclic substituent; R′ and R canform a cycle which optionally comprises a further heteroatom; n is anumber which is less than or equal to
 4. 9. A process according to claim8, wherein the aromatic ether or thioether has formula (I′) where R′represents: a linear or branched, saturated or unsaturated acyclicaliphatic radical containing 1 to 12 carbon atoms; the hydrocarbon chaincan optionally be interrupted by a heteroatom, a functional group and/oroptionally carry substituents; a linear or branched, saturated orunsaturated acyclic aliphatic radical carrying a cyclic substituentwhich may optionally be substituted: said acyclic radical can beconnected to the cycle by a valence bond, a heteroatom or a functionalgroup; a saturated carbocyclic radical or a carbocyclic radicalcomprising 1 or 2 unsaturations in the cycle, and containing 3 to 8carbon atoms; said cycle is optionally substituted; an aromaticcarbocyclic radical containing at least 4 carbon atoms.
 10. A processaccording to claim 8, wherein the aromatic ether or thioether hasformula (I′) in which R′ represents a linear or branched allyl radicalcontaining 1 to 6 carbon atoms.
 11. A process according to claim 8,wherein the aromatic ether or thioether has formula (I′) in whichresidue A represents the residue of an aromatic monocyclic carbocycliccompound containing at least 4 carbon atoms, or the residue of apolycyclic carbocyclic compound, residue: A can carry one or moresubstituents on the aromatic ring.
 12. A process according to claim 8,wherein the aromatic ether or thioether has formula (I′a):

where: n is a number which is less than or equal to 4; Y represents anoxygen atom or a sulphur atom; radical R′ represents a linear orbranched alkyl radical containing 1 to 6 carbon atoms; radical(s) R,which may be identical or different, represent one of the followingatoms or groups: a hydrogen atom a linear or branched alkyl radicalcontaining 1 to 6 carbon atoms a linear or branched alkenyl radicalcontaining 2 to 6 carbon atoms a cyclohexyl, phenyl or benzyl radical alinear or branched alkoxy radical containing 1 to 6 carbon atoms an acylgroup containing 2 to 6 carbon atoms; a radical with formula: —R₁—OH—R₁—COOR₂ —R₁—CHO —R₁—NO₂ —R₁—CN —R₁—N(R₂)₂ —R₁—CO—N(R₂)₂ —R₁—X —R₁—CF₃in said formulae, R₁ represents a valence bond or a divalent, linear orbranched, saturated or unsaturated hydrocarbon radical containing 1 to 6carbon atoms; radicals R₂, which may be identical or different,represent a hydrogen atom or a linear or branched alkyl radicalcontaining 1 to 6 carbon atoms; X represents a halogen atom; radicals Rand R′ placed on two neighbouring carbon atoms may together form withthe carbon atoms they carry a cycle containing 5 to 7 atoms, optionallycomprising a further heteroatom.
 13. A process according to claim 12,wherein the aromatic ether or thioether has formula (I′a) where when nis greater than or equal to 1, radicals R′and R and the two successiveatoms of the benzenic cycle can be bonded together to form an alkylene,alkenylene or alkenylidene radical containing 2 to 4 carbon atoms toform a saturated, unsaturated or aromatic heterocycle containing 5 to 7atoms in which one or more carbon atoms can be replaced by a furtherheteroatom: radicals YR′ and R form a methylenedioxy, ethylenedioxy,methylenedithio or ethylenedithio radical.
 14. A process according toclaim 8, wherein the aromatic ether or thioether has formula (I′) or(I′a) in which: n equals 0 or 1; R′ represents a linear or branchedalkyl radical containing 1 to 6 carbon atoms or a phenyl radical; Rrepresents a linear or branched alkyl radical containing 1 to 6 carbonatoms, or a linear or branched alkoxy radical containing 1 to 4 carbonatoms; radicals YR′ and R form a methylenedioxy, ethylenedioxy,methylenedithio or ethylenedithio radical.
 15. A process according toclaim 1, wherein the aromatic compound is benzene, toluene,isobutylbenzene, anisole, phenetole, veratrole,1,2-methylenedioxybenzene, 2-methoxynaphthalene or thioanisole.
 16. Aprocess according to claim 1, wherein the acylation agent comprisescarboxylic acids and their halide or anhydride derivatives.
 17. Aprocess according to claim 16, wherein the acylation agent has formula(II):

where: R₃ represents: a linear or branched, saturated or unsaturatedaliphatic radical containing 1 to 24 carbon atoms; a monocyclic orpolycyclic saturated, unsaturated or aromatic cycloaliphatic radicalcontaining 3 to 8 carbon atoms; or a linear or branched, saturated orunsaturated aliphatic radical carrying a cyclic substituent; X′represents: a halogen atom; a hydroxyl group; a —O—CO—R₄ radical, whereR₄, which may be identical to or different from R₃, has the same meaningas R₃: R₃ and R₄ may together form a divalent linear or branched,saturated or unsaturated aliphatic radical containing at least 2 carbonatoms.
 18. A process according to claim 17, wherein the acylation agenthas formula (II) in which X′ represents a chlorine atom and R₃represents a linear or branched alkyl radical containing 1 to 12 carbonatoms, the hydrocarbon chain can optionally be interrupted by aheteroatom or by a functional group or it carries substituents, R₃ alsorepresenting a phenyl radical; X′ represents a —O— CO—R₄ radical, inwhich R₃ and R₄ are identical and represent an alkyl radical containing1 to 4 carbon atoms, and optionally carry halogen atoms or a phenylradical.
 19. A process according to claim 17, wherein the acylationagent is selected from: a acetic anhydride; propanoic anhydride butyricanhydride; isobutyric anhydride; trifluoroacetic anhydride; benzoicanhydride; monochloroacetyl anhydride; dichloroacetyl anhydride; acetylchloride; monochloroacetyl chloride; dichloroacetyl chloride; propanoylchloride; isobutanoyl chloride; pivaloyl chloride; stearoyl chloride;crotonyl chloride; benzoyl chloride; chlorobenzoyl chlorides;p-nitrobenzoyl chloride; methoxybenzoyl chlorides; naphthoyl chlorides;acetic acid; benzoic acid.
 20. A process according to claim 16, whereinthe acylation agent is acetic, propanoic, benzoic, monochloroacetyl, ordichloroacetyl anhydride, or benzoyl chloride.
 21. A process accordingto claim 1, wherein the catalyst is a natural or synthetic zeolite. 22.A process according to claim 21, wherein the zeolite is a naturalzeolite selected from: chabazite, clinoptilolite, erionite, mordenite,phillipsite, and offretite.
 23. A process according to claim 22, whereinthe zeolite is a synthetic zeolite comprising: zeolites with aone-dimensional network comprising ZSM-4 zeolite, L zeolite, ZSM-12zeolite, ZSM-22 zeolite, ZSM-23 zeolite, or ZSM-48 zeolite; zeoliteswith a two-dimensional network comprising β zeolite, mordenite, orferrierite; zeolites with a three-dimensional network comprising Yzeolite, X zeolite, ZSM-5 zeolite, ZSM-11 zeolite, or offretite;mesoporous MCM type zeolite.
 24. A process according to claim 23,wherein the zeolite is a β and a Y zeolite.
 25. A process according toclaim 21, wherein the zeolite is used alone or mixed with an inorganicmatrix.
 26. A process according to claim 1, wherein the ratio betweenthe number of moles of aromatic compound and the number of moles ofacylation agent is between 0.1 and
 20. 27. A process according to claim1, wherein the ratio between the number of moles of aromatic compoundand the number of moles of acylation agent is at least
 1. 28. A processaccording to claim 1, wherein the quantity of catalyst is 0.01% to 50%,by weight with respect to the aromatic compound used.
 29. A processaccording to claim 1, wherein the temperature at which the acylationreaction is carried out is in the range 20° C. to 300° C.
 30. A processaccording to claim 1, wherein the reaction is carried out at atmosphericpressure.
 31. A process according to claim 1, wherein the reactionmixture passes through the catalytic bed from bottom to top and at theoutlet.
 32. A process according to claim 31, wherein the degree ofconversion is more than 20%.
 33. A process according to claim 1, whereinthe linear velocity of the liquid stream over the catalytic bed isbetween 0.1 and 10 cm/s.
 34. A process according to claim 1, wherein theresidence time of the material stream on the catalytic bed is between 15minutes and 15 hours.
 35. A process according to claim 1, wherein whenthe reaction is over, a liquid phase comprising the acylated aromaticcompound is recovered.